The present invention relates to apparatus for imaging photographic film or the like, and more particularly to a scanning exposure slit for a shuttle style film gate used in a film transport. As used herein, the term "film" is intended to mean any type of image recording medium, including photographic film, thermal media, dye transfer media and the like, and is not to be construed only as photographic film.
In order to record high quality images on photographic film or other media for the production of movies or slides, film recorders are used. In a conventional film recorder, a light beam from a cathode ray tube ("CRT") or the like is controlled by a deflection system to scan across a stationary frame of photographic film to expose the film with an image. Typically, the images are generated by a computer for the production of slides, transparencies, photographs or the like. Alternatively, the images can comprise natural images acquired by a scanner or television camera for subsequent processing by a computer.
Known film recorders, such as those sold under the trademark SOLITAIRE.RTM. by Management Graphics, Inc. of Minneapolis, Minn., U.S.A., typically include a light source such as a CRT for producing a beam, a deflection system for scanning the beam across the face of the CRT, a system control and central processor unit ("CPU") for controlling the deflection system, and a camera (i.e., "film transport"). The later component may include a film transport body, lens, lens mounting assembly, aperture plate, film plate, and film transport mechanism. One type of film transport mechanism that is widely in use is a shuttle style film gate. Such transports are manufactured, for example, by Oxberry Corporation of Mamaroneck, N.Y., U.S.A.
On a Solitaire.RTM. film recorder, an image to be recorded is first written on the phosphor of the CRT by deflecting an electron beam in a raster pattern and modulating the intensity of the beam. This process is analogous to the creation of a television picture. Alternatively, the image can be written on the CRT using well known time modulation techniques, wherein the beam intensity is constant but the time the beam is kept at each point is varied depending on the exposure required.
The resulting pattern (the "object image") on the CRT is optically imaged onto photographic film by the film transport, which contains the required optics and mechanism to advance the film to successive frames. Other types of light sources can be substituted for the CRT in a film recorder. Examples include fiber optic sources, lasers and focused light impinging a rotating drum wherein one or more rotations are completed for each scan line.
One problem that has arisen when light is scanned onto the film one line at a time is that the light for one line will bleed over into other lines. This results in fogging of the image or a halo effect that is detrimental to the final image.
In a shuttle style film gate, such as that used in the aforementioned Oxberry film transport, successive frames of film are moved into an exposure area one at a time. The film is transported through the exposure area using pins which engage sprockets on the film. The pins pick up the film at one end of the exposure area and transport it to the other end, where the new frame is then lowered (or raised) onto fixed pins which precisely register the frame for exposure. During exposure, the moving pins are returned to the first end of the exposure area where they will be ready to pick up the film after exposure of the current frame, in order to transport the next successive frame into position for exposure. The moving pins can be driven by a stepper motor, which can be controlled by an electronic controller (e.g., CPU) in order to properly synchronize the film transport and exposure operations.
It would be advantageous to provide such a shuttle style film gate with a mechanism for reducing the fog and halo effects which result when light from one line being scanned bleeds over into other lines. It would be further advantageous to provide such a mechanism that can be fitted onto a conventional shuttle style film gate with minimal modification. It would be still further advantageous to provide such a mechanism that takes advantage of the motion already provided by the film gate in order to overcome the problems of fog and halo.
The present invention provides a scanning exposure slit mechanism having the aforementioned and other advantages.